The present invention relates to ethylene copolymers having a novel structure and a process for the production thereof. More particularly, it is concerned with ethylene copolymers which comprises a straight chain base polymer of an ethylene unit with an unsaturated carboxylic acid or its ester unit orientated in a random arrangement in the ethylene base polymer and, if desired, further with a small amount of alkyl side chains bonded to the ethylene base polymer, and to a process for efficiently producing the above ethylene copolymers.
As copolymers of ethylene and unsaturated carboxylic acid or its esters (e.g., acrylic acid esters), copolymers produced by the high pressure radical polymerization method or the low pressure Ziegler method have been known. Copolymers produced by the high pressure radical polymerization method have such a structure that the unsaturated carboxylic acid or its ester radical is orientated in the ethylene chain in a random arrangement. It is known, however, that in accordance with the high pressure radical polymerization method, monomers are not copolymerized in a straight chain arrangment; there are obtained only branched copolymers. On the other hand, in copolymers produced by the low pressure Ziegler method using titanium, zirconium and a vanadium compound as catalyst components, the unsaturated carboxylic acid or its ester is bonded to the ethylene polymer chain in a block copolymer arrangement. That is, by any of the conventional polymerization method including the high pressure radical polymerization method and the low pressure Ziegler method, copolymers in which the ethylene unit and the unsaturated carboxylic acid or its ester unit are arranged in a random configuration have not be obtained.